Studies on anoxic metabolism of mammalian brains are seriously hampered by the high degree of obligate oxygen dependence of this tissue. Turtle brains are unique in being able to maintain their functional integrity after many hours of total anoxia. It is proposed to use the turtle brain as a model to examine cerebral anaerobic processes. Specifically, the role and nature of anaerobic energy supply both cellular and systemic, the relationship of cell energy supply to brain electrical activity and to extracellular K activity, the role of increased CO2 in cell metabolism and the role of decreased temperature in enhanced survival. We will test the hypothesis that there is a capability within turtle brain to survive prolonged anoxia which was modified or lost during mammalian evolution. Identification of this capability and development of a greater understanding of anaerobiosis and its relation to electrophysiology and viability of CNS may present a key to ultimate survival or prevention of human anoxic/ischemic brain injury.